408 
DIGESTIVE ORGANS AND FOOD 
The esophagus is a nearly straight tube connecting the 
mouth with the stomach. It passes through the diaphragm 
(Figure 395), enlarges, and becomes the stomach. As 
soon as one swallows, control of the food is lost, and further 
action becomes involuntary. Two sets of muscles, one ex¬ 
tending lengthwise, the other around the esophagus, act 
together in forcing the food 
or water into the stomach. 
This explains why we can 
drink from a brook when 
the head is much lower 
than the stomach. 
Stomach. — In man the 
stomach is the largest sec¬ 
tion of the digestive tube, 
and it has a capacity of 
about three pints. It is usually described as pear-shaped 
although there is much variation in its form (Figures 370 
and 371). At the point where the esophagus joins the 
stomach there is a muscular ring (< cardiac valve, kar'di-ak) 
which ordinarily prevents, the food from passing again into 
the esophagus. In vomiting, this valve be¬ 
comes relaxed. The opening at the larger 
and lower end of the stomach is guarded 
by a similar valve {pyloric, pi-lor'ik) which 
serves to retain the food in the stomach Figure 370 .— Pear- 
until certain digestive changes have taken shaped Human 
place. Stomach - 
The intestine has two parts, a small, much coiled tube 
about an inch in diameter and about twenty feet long called 
the small intestine, and a large section about five feet long 
and four inches in diameter, bent in a rough f| shape and 
called the large intestine. At the junction between these two 
regions projects a short sac, the vermiform appendix (ver'- 
mi-form ap-pen'diks). The disease called appendicitis 
Figure 369 . — Permanent Teeth. 
